The present invention relates generally to an optical reflector system for a lamp, designed to create a uniform, high intensity beam of light suitable for use as an automobile headlight, a flashlight, or the like.
Existing flashlights or headlights include a suitable light source such as a filament light bulb or gas discharge lamp located at the focus of a parabolic rear reflector for directing light beams emitted from the source forwardly through a suitable window at the front end of the flashlight or headlight. One problem with such devices is that the light source is not a true point, but is in fact an elongated line-type source, so that the emitted light is not all directed in a parallel, cylindrical beam of light in the desired illumination direction. Also some wide angle rays radiate outwardly to the side of the device, reducing the effective beam intensity and causing undesirable glare. In some cases, such as underwater use or use in foggy conditions, wide angle side scattered light can cause back scattering into the eyes of the user, significantly reducing visibility.
Some attempts have been made in the past to reduce these problems. For example, in U.S. Pat. No. 3,796,886 of Freeman describes a sealed beam lamp in which a light source is located at the focus of a first rear reflector of parabolic shape, and a second rear reflector of elliptical shape also has a focal point coincident with the light source. A spherical front reflector has an origin at the light source and an aperture located at the second focal point of the elliptical reflector. A plano-convex lens is located at the center of the front window of the lamp. The front reflector is positioned to intercept all diverging light rays originating from the source which would otherwise pass through the front opening of the parabolic reflector without reflection. The intercepted rays are directed back to the elliptical reflector, where they are reflected back again through the aperture of the front reflector, and focused by the lens.